Hand tools, such as screwdrivers with gear mechanisms, or the like, are commonly in use in various fields, including the medical instrument field where this invention is useful. Those tools have an elongated handle with gear-type teeth or the like within the handle and with a spring pressing on the teeth to hold the teeth in mutual engagement while the handle is being rotated to apply a torque to a work piece such as a screw. Also, in that arrangement, the gear teeth may be held together for a transmission therebetween of a maximum torque applied to the work piece Even further, the tool might have an adjustment which permits adjusting the force of the spring on the gear teeth to thereby adjust the maximum torque transmitted through the handle and to the work piece.
The present invention provides an adjustable control for applying selective forces on the gears or the like and doing so with a spring which forces on the gears in accord with the setting of the adjustable control.
Still further, the aforementioned adjustable control can have indicia thereon, such as graduation markings, so that the adjusted position of the control can be readily detected by the user and thus the control can be set in a desired position for effecting the desired spring force on the gears or those items which are transmitting the torque.
In that arrangement, it is desirable to have the adjustable control rotatable on the handle so that it can be set in the desired position but also have the control limited in its adjustable positioning so that it will operate exclusively within only a range of adjustment and not exceed its positioning to where it could actually become disconnected or otherwise fail in its operation. The entire arrangement is such that the operator can set the adjustable control to one of various selectable positions, and the operator can be assured that each time the control is set in that position that the desired maximum torque will be transmitted by the tool, and the transmitted torque will be limited to that one maximum amount in accord with that one setting for the adjustable control.